[Strawbale] Forced air

[Mark BP / Low Energy Design Ltd]

Don + all -

I'm prepared to believe that forced air doesn't create any more of a 
dust problem.

Re energy consumption, though, the situation doesn't seem to me to be so 
simple.

A high-performance furnace ought, all other things being equal, to 
achieve at least as good a system efficiency as a high-performance 
boiler.  However, there are 2 other factors which need to be taken into 
account:
(1) At least compared to properly-designed underfloor systems, there is 
likely to be a less consistent air temperature distribution within 
living spaces, which will tend to raise the temperature that people need 
to be comfortable.
(2) A higher rate of air movement also means that the temperature 
required for comfort will be higher.  This is particularly true close to 
the registers, but also elsewhere in the living space.

One not-particularly-scientific piece of evidence.  Back in Britain, I 
used to be able to keep daytime thermostat settings (at least when my 
wife wasn't in) down to 16 or 17 deg C.  Here in Saskatchewan, I 
generally find that I need 18.5, 19 or even 20 deg C for my own comfort. 
  I haven't changed my activities significantly, nor my level of 
clothing.  (Of course, it may just be that I'm getting old...)

That sort of difference in required temperature results in a real 
difference in energy consumption - somewhere between 5% and 10% 
according to my rough calcs of the impact on heating degree days here in 
SK, and a bigger percentage difference in more maritime climates.

mark



dfugler at cmhc-schl.gc.ca wrote:

>Tigrrr Lily et al,
>
>You said: "I may be have to have forced air conditioning, but I will NEVER 
>have forced air heat, because besides the fact that it is highly 
>inefficient compared to almost anything else, it sprays dust and allergens 
>all over the place."
>
>There are many reasons not to like forced air over alternatives. Mark 
>mentioned the possible irritation of moving air, the noise, the British 
>perception that they are "cheap and nasty", etc. There are probably 
>others. You can choose another heat distribution system that appeals to 
>you if you don't like forced air.
>
>However, I still challenge your assertion that they are dusty and energy 
>inefficient. For the last ten years, I have been looking at the testing of 
>houses for particles and dust, and there are no credible research findings 
>that show forced-air houses are dustier (or more expensive to heat). 
>
>Don Fugler
>CMHC Policy and Research 
>  
>
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